https://bugs.winehq.org/show_bug.cgi?id=43193
--- Comment #6 from Dan Kegel dank@kegel.com --- +relay shows it's trying to do something with pipes.
grep CreateFile on the +relay log shows
0030:Call KERNEL32.CreateFileW(071997c0 L"C:/msys64/usr/share/terminfo/6e/nansi.sys",40000000,00000000,00000000,00000003,00000080,00000000) ret=00526812 0030:Ret KERNEL32.CreateFileW() retval=0000013c ret=00526812 002b:Call KERNEL32.CreateFileW(07182e48 L"\\.\pipe\{864f5d44-2139-4170-b7e6-2d379d479040}",c0000000,00000000,00000000,7f8400000003,40000000,00000000) ret=010304d0 002b:Ret KERNEL32.CreateFileW() retval=ffffffffffffffff ret=010304d0 002f:Call KERNEL32.CreateFileW(07183018 L"\\?\C:\users\dank\Start Menu\Programs\MSYS2 64bit\MSYS2 MinGW 32-bit.lnk",80000000,00000001,00000000,00000003,00000000,00000000) ret=7f84ada81fc5 002f:Ret KERNEL32.CreateFileW() retval=00000130 ret=7f84ada81fc5 ... 003d:Call KERNEL32.CreateFileW(0023d640 L"C:\msys64\msys2_shell.cmd",80000000,00000003,00000000,00000003,00000000,00000000) ret=7f2856508fc5 003d:Ret KERNEL32.CreateFileW() retval=00000054 ret=7f2856508fc5 003f:Call KERNEL32.CreateFileW(600010038 L"\\.\pipe\msys-dd50a72ab4668b33-lpc",c0000000,00000003,180275ec0,100000003,2020202000020000,00000000) ret=180165330 003f:Ret KERNEL32.CreateFileW() retval=ffffffffffffffff ret=180165330 ... 003f:Call KERNEL32.CreateFileA(ffffb810 "\\.\pipe\msys-dd50a72ab4668b33-62-pipe-0x1",40000080,00000000,180275f20,00000003,7f3440000000,00000000) ret=1800eff49 003f:Ret KERNEL32.CreateFileA() retval=00000110 ret=1800eff49 002b:Call KERNEL32.CreateFileW(07180378 L"\\.\pipe\{864f5d44-2139-4170-b7e6-2d379d479040}",c0000000,00000000,00000000,7f8400000003,40000000,00000000) ret=010304d0 002b:Ret KERNEL32.CreateFileW() retval=ffffffffffffffff ret=010304d0 002b:Call KERNEL32.CreateFileW(07180378 L"\\.\pipe\{864f5d44-2139-4170-b7e6-2d379d479040}",c0000000,00000000,00000000,7f8400000003,40000000,00000000) ret=010304d0 002b:Ret KERNEL32.CreateFileW() retval=ffffffffffffffff ret=010304d0 ...
Looks like it's in their fork of cygwin.